1. Field of the Invention
The present invention relates to a semiconductor processing apparatus and, more particularly, to an electron cyclotron resonance plasma CVD (to be referred to as an ECR plasma CVD hereinafter). The present invention further relates to a method of cleaning a semiconductor processing apparatus.
2. Description of the Related Art
A silicon oxide film is formed as, e.g., an insulating interlayer in a manufacturing process for a semiconductor device. A silicon oxide film is required for various properties such as feasibility of low-temperature film deposition, a small internal stress of the film, a low etching rate, a good film thickness distribution, good step coverage, and an excellent water permeability resistance.
As a film deposition method for fully satisfying these conditions, there is an ECR plasma CVD method. FIG. 1A is a schematic view showing a conventional ECR plasma CVD apparatus 10. Referring to FIG. 1A, reference numeral 11 denotes a plasma processing chamber constituted by an airtight vessel. A turbo molecular pump 13 is connected to this plasma processing chamber 11 via a gate valve 12. A dry pump 15 is connected to this turbo molecular pump 13 via a valve 14. A molecular drag pump may be used instead of the turbo molecular pump 13.
The film deposition process according to the ECR plasma CVD method is performed as follows. First, the gate valve 12 are opened. In this condition, the turbo molecular pump 13 and the dry pump 15 are driven to keep the interior of the plasma processing chamber 11 in a high vacuum condition. The high vacuum condition is, for example, pressure of several mTorr. In the plasma processing chamber 11 under this high vacuum condition, a target object is placed, and a process gas is introduced to perform a film deposition process.
In the above film deposition process, reaction products are deposited not only on the target object but also on any surface of the inside of the plasma processing chamber 11. To remove the reaction products on the plasma processing chamber 11, so-called in situ cleaning is regularly performed inside the plasma processing chamber 11. A plasma for cleaning is generated in the plasma processing chamber 11 to remove reaction products deposited inside the plasma processing chamber 11 by etching. Such a cleaning process is normally performed in an atmosphere of a higher pressure than the pressure of a normal film deposition process. The pressure for the cleaning process is, for example, several Torr.
The pressure for the cleaning process, however, is higher than an maximum pressure 0.5 m Torr in which the turbo molecular pump 13 can operate. Therefore, the turbo molecular pump 13 must be temporarily stopped in the above in situ cleaning. However, if the turbo molecular pump 13 is stopped every cleaning process, the production efficiency is greatly decreased because the start and stop of the normal turbo molecular pump 13 require 15 minutes and 10 minutes, respectively.
To avoid the above disadvantage in the prior art, a bypass exhaust pipe 16 is connected to between a plasma processing chamber 11 to a pipe which couples a valve 14 to a dry pump 15, as shown in FIG. 1B. A valve 17 is provided on the bypass exhaust pipe 16.
In an ECR plasma CVD apparatus 10' having such a bypass, in a cleaning process, the gate valve 12 is closed, and the valve 17 is opened to perform an exhaust operation by the bypass exhaust pipe 16 and the dry pump 15 while a turbo molecular pump 13 is activated. With this operation, the internal pressure of the turbo molecular pump 13 is kept at a high vacuum degree, so that the normal operation of the turbo molecular pump is ensured. Accordingly, the cleaning process can be executed without stopping the turbo molecular pump 13.
When the bypass exhaust pipe 16 and the valve 17 (to be referred to as a bypass line hereinafter) are provided like in the above ECR plasma CVD apparatus 10', however, generation source, and a target object is more likely the apparatus is bulky and complicated due to the bypass line.
To set the interior of the plasma processing chamber 11 to the high vacuum condition, it is preferable to arrange the turbo molecular pump 13 near the plasma processing chamber 11 as close as possible. Therefore, the gate valve 12 is arranged very near the plasma processing chamber 11. Owing to this arrangement, reaction products tend to attach to the inside of the gate valve 12 to cause generation of particles, resulting in a decrease in yield. Moreover, since the gate valve 12 is near the plasma processing chamber 11, an O-ring, a bearing, and the like of the gate valve 12 may be damaged by a plasma generated in the plasma processing chamber 11 in film deposition, decreasing the reliability and the production efficiency.